(1) Field of the Invention
The present invention relates to a novel polyorganosiloxane suitable for the modification of silicone rubbers and synthetic resins.
(2) Description of the Prior Art
Heretofore, a fluorine-containing group has been introduced into silicone rubbers for the purpose of improving oil resistance and solvent resistance. A typical example of the fluorine-containing group is a 3,3,3-trifluoropropyl group, and the fluorine-containing group is usually introduced into a pendant site (branch site of a polysiloxane chain). Such fluorosilicone rubbers have been used singly and in the form of blends and copolymers of these rubbers and ordinary silicone rubbers.
Furthermore, polyorganosiloxanes have been used in synthetic resins with the intention of providing molded articles of the synthetic resins with interfacial characteristics such as water repellency, release properties and stain resistance as well as other characteristics such as heat resistance which the polyorganosiloxanes have. In these polyorganosiloxanes, the straight-chain polysiloxanes are mainly used. The polysiloxane compound not having any group which is reactive with a synthetic resin is introduced into the synthetic resin by blending them, and the polyorganosiloxane having the group which is reactive therewith is introduced thereinto by chemical bond. The polyorganosiloxane can be also used as a raw material of graft polymers for the modification of the synthetic resin to which much attention is paid of late, and particularly in this case, the so-called monofunctional polyorganosiloxane has been used in which one terminal alone has a functional group and another terminal is terminated with an alkyl group.
However, when the fluorine-containing substituent is introduced at the pendant site as in conventional silicone rubbers, the fluorine-containing substituent is uniformly present in molded or coated products, and therefore a great deal of the fluorine-containing substituent is required to obtain the expected effect. In addition, there are also troubles due to poor miscibility and a problem such as the bad influence of the substituents on other physical properties.
Also when the polyorganosiloxane is used for the purpose of improving the specific characteristics of the, synthetic resin, the improvement depends upon the function of the polysiloxane. Thus, the degree of improvement of the synthetic resin is insufficient in view of the fact that the demand of the specific characteristics is now increased. Moreover, in order to obtain the characteristics sought, a great deal of the polyorganosiloxane is required, which leads to the problem that the other physical properties are adversely affected. The monofunctional polyorganosiloxane also has similar disadvantages, because the other terminal of the molecular chain which has no functional group for the synthetic resin is terminated with the trimethylsiloxy group. In addition, specific properties such as oil repellency are scarcely improved by the polydimethylsiloxane alone in which the other terminal is terminated with an alkyl group.